This invention relates to molten metal pumps and more particularly to an impeller system suited for use in a molten metal pump. While references may be made herein to molten aluminum, this is only used by way of example and not to limit the invention to molten aluminum pumps, since the pump and impeller systems disclosed herein may be used for pumping other molten metals.
When molten metal is processed, it is often necessary to move molten metal within a particular vessel or container and from one location to another. Partially or wholly submersed pumps are generally used to accomplish this movement of molten metal.
In many applications, a rotatable impeller is located within a pumping chamber and utilized as part of the pumping system. The rotation of the impeller within the pumping chamber draws in molten metal and forces it out in a direction dictated by the geometry and outlet of the pumping chamber and molten metal pump.
Impeller systems are typically supported and mounted for rotation by a shaft connected to a drive motor which is located on a platform typically maintained above the surface level of the molten metal in the vessel or container.
Molten metal may be one of the more difficult environments in which to maintain a pump and impeller due to the heat and corrosive factors within the molten metal. The submerged components of these pumps are typically made of graphite, ceramics or similar materials due to the ability of these types of material compositions to withstand the heat and corrosive effects of the molten metal environment. Furthermore, in many applications there are large pieces of metal which are not melted and which may clog a molten metal pump if allowed to enter and then it gets trapped therein.
Once a pump is clogged or needs to be replaced or serviced, replacement is a time consuming exercise. First the pump must be removed from the molten metal, which generally causes down time of the metal furnace if that is the location of the pump. Then the pump along with the molten metal contained thereon must be allowed to sufficiently cool to allow it to be disassembled. Once the deteriorated components are sufficiently cool, the molten metal built up on the various pump surfaces must be sufficiently removed to allow disassembly and/or reuse of the pump components. Then the pump must be reassembled with the combination of old components or parts, along with the replacement parts. The down time of a molten metal pump may be as much as two to three days before it is operational again, which illustrates the importance of increasing the useful life of the pumps.
It may also be desirable in some embodiments of the invention to configure the impeller so that the interior cavity is more open with greater clearances, than for instance, impellers which include individual conduits or apertures through which the molten metal flows.
It is an object of this invention to provide a pump impeller system which is relatively efficient and relatively less prone to clogging by particles and other solid materials.